1. Field of the Invention
This invention relates to extermination of undesirable organisms in soil, and particularly to nematode extermination in lawn soil by heating.
2. Background of the Invention
Nematode infestation of lawns has long been an intractable problem. Present pesticide chemicals that are environmentally acceptable are ineffective. Nematodes can live relatively deep in the soil, for example over 15 cm (6″), and thus cannot be easily reached with pest control measures.
Prior attempts to kill soil infestations of various types using heat generally require scooping a top layer of soil into a heating oven or onto a belt with a burner that cooks the soil to a sterilizing temperature while turning and breaking the soil for even heating. See for example U.S. Pat. No. 5,553,414. This is expensive in terms of both equipment and energy, and is totally disruptive. It is impractical for nematodes in lawns because it would destroy an in-ground sprinkler system and other underground utilities. It could not be used near trees or shrubs because it would either destroy the roots or be damaged and stopped by them. It is impractical due to the massive amount of soil that must be moved and processed to reach the lowest nematodes. The returned soil must be re-graded and tamped. Additionally, these types of soil lifting and cooking machines pose a fire hazard. They use high temperatures from fuel burners in order to heat the lifted soil fast enough to allow the machine to move along and finish the job in a reasonable time. The driver cannot sit in one spot for hours. Lifting the soil aerates it in the process facilitating ignition of organic materials such as humus, grass and twigs. Heating soil hotter than necessary destroys some beneficial soil components including organics. Thus, an improved nematode extermination method is needed.